There is a great need for an inexpensive method for detecting adulteration and determining exact origin of products containing alcohols or sugars. For example, geographic and biological origins of wine products are important factors for determining their value. Consequently, consumers are concerned about the possibility of adulteration, especially regarding more expensive wines. Adulteration may be perpetrated during the production of the wine by adding undesired grape material or even sugars from other sources such as sugar beets. Furthermore, wine can be adulterated by diluting the final product with cheaper, lower quality, wines.
To address this problem, in 1990 the European wine industry adopted a method for detecting wine adulteration using Site-Specific Natural Isotope Fractionation-Nuclear Magnetic Resonance (SNIF-NMR). The SNIF-NMR measures relative deuterium concentration and specific deuterium-site locations in wine ethanol molecules, primarily to detect adulteration with beet sugar. The SNIF-NMR method, however, requires expensive instruments and the procedure is relatively imprecise.
For example, for measurements taken with the standard NMR method, as shown in FIG. 1, the repeatability for 2H-NMR is 0.3 ppm and the effect of enrichment is 0.1 ppm for 0.1% vol. Using 2-fold standard deviation as criteria for repeatability (0.6 ppm), the detection threshold is calculated to approximately 0.6% vol. More specifically, the results for SNIF-NMR method suggest that measured difference between grape and beet sugar is only approx. 3 ppm vs. TMU for methyl-site isotope composition. Since these values are close and have a relatively wide range, e.g., 99 to 106 ppm vs. TMU for grape, and 87.5 to 97.5 ppm vs. TMU for beet sugar, it can be challenging, if not impossible, to determine botanical origin without comparing to results from a database containing data for unadulterated wines. In other words, because of the low sensitivity of the SNIF-NMR method and because the measurement results alone cannot be used to reliably detect adulteration by sugars for fermentation from non-grape sources, it is necessary to create a database for storing results from wine samples to be used for comparison.
On the other hand, the results from tests conducted according to the present invention suggest that the effect of enrichment is about 7% for each 10% of the enrichment for absolute isolated ethanol from wine ethanol with a standard deviation of 1.34%, and the effect of enrichment is 0.7% for each % vol. of ethanol from chaptalization (calculated for wine with 10% vol. alcohol). If a 2-fold standard deviation is used as a criteria for repeatability (2.68%), it should be possible to detect values as low as approximately 0.38% vol. for wine ethanol.
Another method that is widely used for authentication of food products is based on measuring the oxygen stable isotope ratio. This method, however, has limited applicability detecting only sweetening or watering of liquid food products, but not the source of the original material. This analysis generally includes extracting the oxygen and its stable isotopes, and measuring the 18O/16O isotope ratio. The extraction of oxygen usually includes a carbon-dioxide molecular equilibration or pyrolysis.
Thus, there is a need for a method for determining the origin of alcohol or sugar containing products that is accurate, portable, and inexpensive.